Lateral damping apparatus between a truck and a railway car body have been used in the past. Some patents disclosing such apparatus include those issued to Cardwell U.S. Pat. No. 3,397,652; Baade U.S. Pat. No. 2,241,757 and Dobson U.S. Pat. No. 3,628,465. In general, lateral damping apparatus used heretofore have provided damping proportional to the lateral forces applied thereto.
U.S. Pat. No. 3,397,652 is directed to a railway truck bolster dampener. There is provided the laterally extending cylinder 41. The rod 33 having a collar 37 fits in an opening 39 in one end of the cylinder 41. The center of the bell crank 17 is pivotally mounted by the pin 22 between the lugs 23 which extend upwardly from the rack 25. The rack 25 is rigidly secured between the lower portion of the side frames 5 and 7 below the bolster.
U.S. Pat. No. 2,241,757 is directed to a vehicle system. FIG. 19 shows the use of a dampener member 169 to provide an additional lateral motion restrictive mechanism. The mechanism 169 is clearly seen in FIGS. 18 and 23 and in FIG. 19 and 20, it appears that such is merely directed to a spring-like device.
U.S. Pat. No. 3,628,465 is directed to stabilizing high speed railway trucks. The dampening mechanism 50 which is a double-acting hydraulic unit. The unit 50 includes a cylinder member 51 which is pivotally connected at the pivot point 52 to the lower bolster member 22 and further includes a piston member 53 pivotally connected at the pivot point 54 to the upper bolster member 23. This does provide for the laterally extending dampening units as provided in the present invention.
U.S. Pat. No. 1,973,816 is directed to vehicle roller mountings and although directing itself to other inventive elements, it does provide for the pre-loaded springs 27 shown in FIG. 2 which may be thought of as laterally extending dampening units, although not in the same type of mechanism structure as provided in the present invention.
In recent years, passenger rail car suspensions have been designed to optimize the ride comfort for continuous input forces, such as those generated by rail joints every 39 feet. Computer simulations have been used to establish the degree of critical damping necessary for the best ride with an appropriate spring system. With the expanded use of continuously welded rails with joints every 1,000 feet or more, the nature of the track initiated disturbance has changed from a primarily periodic input to a random input due to switches, interlocks, track discontinuities or transitions.
In returning the suspension system for the newer requirements, it is desirable to retain a minimum damping for small and sometimes periodic disturbances. As the magnitude of the random disturbance increases, it is desirable to increase the damping in higher proportions to reduce overshoot of the car body due to the lateral disturbance. In other words, it is desirable to provide light damping except in response to a heavy disturbance, at which time proportionally higher damping is applied as the disturbance becomes greater.